Systems and Methods for In Situ Monitoring of Cement Slurry Locations and Setting Processes Thereof

ABSTRACT

Optical analysis systems may be useful in monitoring fluids relating to cementing operations in or near real-time, e.g., for location and/or the status of a cement setting process. For example, method may involve containing a cement slurry within a flow path, the cement slurry having a chemical reaction occurring therein; and optically interacting the cement slurry with an integrated computational element, thereby generating an output signal corresponding to a characteristic of the chemical reaction.

BACKGROUND

The present invention relates to optical analysis systems and methods for analyzing fluids and, in particular, to systems and methods for monitoring fluids relating to cementing operations in or near real-time.

Cementing operations are often used in wellbores for, inter alia, supporting casings and liners, providing zonal isolation, and protecting the casing from corrosive formation fluids. In such operations, it is often important to precisely know the location, characteristics, and setting status of cement slurries as they circulate and set in wellbores or other annuli therein. In situ analysis of cement slurries during cementing operations is often not achievable with conventional monitoring systems, which are incapable of operation in extreme environments such as downhole applications. Accordingly, the location, characteristics, and setting status of cement slurries are often required to be extrapolated from laboratory data, calculations of volumes to be filled, and calculations based on the conditions in the wellbore (e.g., temperature).

After the cementing operation has completed, the location, characteristics, and setting status of cement slurry (or set cement) can be analyzed via logging techniques, which are time-consuming and costly. For example, if the cementing operation was successfully performed (e.g., the proper locations were cemented) and the cement is sufficiently set, subsequent subterranean operations can be performed (e.g., drilling operations, fracturing operations, completion operations, and the like). However, if an aspect of the cementing operation was incorrect, remedial operations are often necessary.

For example, if the cement is not sufficiently set, the operator allows for additional setting time and then runs another logging operation, which further contributes to costs and nonproductive time.

In another example, if too much cement slurry was added, a drillout operation may be required, which is particularly prevalent in reverse cementing where the cement is pumped from the annulus side. In other instances, if too little cement slurry was added, another cementing operation may be needed.

These issues can be especially complex in normal primary cementing operations where the cement slurry is pumped down the casing and up the annulus. Generally, the cement slurry formulations are designed so that the ‘lead’ slurry (i.e., uppermost slurry after placement in the annulus) is of lower density than the ‘tail’ slurry that is the bottommost slurry placed near the bottom of the annulus. Proper placement of the ‘lead’ slurry behind casing and the sufficient setting of the cement near the casing shoe (i.e., near the bottom of the casing) are important for the casing to withstand pressures of the initial pressure test and subsequent drilling that are performed.

In other cementing operations, e.g., some remedial operations to plug thief zones, two fluids are utilized that when contacted viscosify and plug high permeability regions in the wellbore. Pumping calculated volumes is often insufficient to assure operation efficacy, which can lead to additional remedial operations and the use of high volumes of expensive fluids. Accordingly, in situ monitoring of the location of each of these fluids may reduce the cost and time associated with such remedial cementing operations.

As a whole, cementing operations are often performed multiple times during the lifetime of a well. Therefore, in situ analysis of cement slurries and/or set cements may have a compounding effect on reducing the cost and time associated with the drilling and maintenance of a well.

SUMMARY OF THE INVENTION

The present invention relates to optical analysis systems and methods for analyzing fluids and, in particular, to systems and methods for monitoring fluids relating to cementing operations in or near real-time.

One embodiment of the present invention is a method that comprises containing a cement slurry within a flow path, the cement slurry having a chemical reaction occurring therein; and optically interacting the cement slurry with an integrated computational element, thereby generating an output signal corresponding to a characteristic of the chemical reaction.

Another embodiment of the present invention is a method that comprises flowing a series of fluids through a flow path, the series of fluids comprising a spacer fluid followed by a cement slurry; and optically interacting at least one of the series of fluids with an integrated computational element, thereby generating an output signal corresponding to a characteristic of the at least one of the series of fluids.

Yet another embodiment of the present invention is a system that comprises a flow path containing a cement slurry; and at least two optical computing devices arranged in the flow path for monitoring the cement slurry, each of the at least two optical computing devices independently having at least one integrated computational element configured to optically interact with the cement slurry and thereby generate optically interacted light, and at least one detector arranged to receive the optically interacted light and generate an output signal corresponding to a characteristic of the cement slurry.

The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the preferred embodiments that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of the present invention, and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to those skilled in the art and having the benefit of this disclosure.

FIG. 1 illustrates an exemplary integrated computation element, according to one or more embodiments.

FIG. 2 illustrates a block diagram non-mechanistically illustrating how an optical computing device distinguishes electromagnetic radiation related to a characteristic of interest from other electromagnetic radiation, according to one or more embodiments.

FIGS. 3A-B illustrate an exemplary system for monitoring a fluid, according to one or more embodiments.

FIG. 4 illustrates another exemplary system for monitoring a fluid, according to one or more embodiments.

DETAILED DESCRIPTION

The present invention relates to optical analysis systems and methods for analyzing fluids and, in particular, to systems and methods for monitoring fluids relating to cementing operations in or near real-time.

The exemplary systems and methods described herein employ various configurations of optical computing devices, also commonly referred to as “opticoanalytical devices,” for the real-time or near real-time monitoring of fluids in order to ascertain the location of a cement slurry and/or the status of a cement setting process. In operation, the exemplary systems and methods may be useful and otherwise advantageous in determining that a cement slurry has been properly placed, for example, in a wellbore, by monitoring a characteristic of the cement slurry and/or a spacer fluid introduced into the wellbore before or after the cement slurry. In other embodiments, the systems and methods may provide a real-time or near real-time determination of cement setting process kinetics, including the concentration of unreacted reagents and/or resultant products.

The optical computing devices, which are described in more detail below, can advantageously provide real-time or near real-time monitoring of a cement slurry or other fluid relating thereto (e.g., a spacer fluid) and chemical reactions occurring therein that cannot presently be achieved with either onsite analyses at a job site or via more detailed analyses that take place in a laboratory. A significant and distinct advantage of these devices is that they can be configured to specifically detect and/or measure a particular characteristic of interest of a fluid or other material, thereby allowing qualitative and/or quantitative analyses of the fluid to occur without having to extract a sample and undertake time-consuming analyses at an off-site laboratory. With the ability to undertake real-time or near real-time analyses, the exemplary systems and methods described herein may be able to provide some measure of proactive or responsive control over the cement slurry location, provide some measure of cement slurry loss into the subterranean formation as an indicator of wellbore damage, eliminate time-consuming wireline operations that analyze the progress of the setting processes of cement slurries, mitigate drill-out operations as a result of excess cement slurry introduction into the wellbore, enable the collection and archival of information relating to cement setting processes in conjunction with operational information to optimize subsequent operations, and/or enhance the capacity for remote job execution.

Those skilled in the art will readily appreciate that the systems and methods disclosed herein may be suitable for use in the oil and gas industry since the described optical computing devices provide a relatively low cost, rugged, and accurate means for monitoring fluids and chemical reactions occurring therein in order to facilitate the efficient management of wellbore operations involving cement slurries. It will be further appreciated, however, that the various disclosed systems and methods are equally applicable to other technology or industry fields including, but not limited to, the construction industry, industrial applications, mining industries, or any field where it may be advantageous to determine in real-time or near real-time the status of the cement setting processes or other similar chemical reactions.

The optical computing devices suitable for use in the present embodiments can be deployed at any number of various points within a flow path to monitor a fluid, including, the location of a cement slurry, the location of a spacer fluid introduced before or after a cement slurry, and/or the status of the cement setting process. It should be noted that the location of a material of interest can be derived from detecting a characteristic of interest with an optical computing device having a known location (approximate or exact) or using two or more optical computing devices having known relative locations to each other. Depending on the location of the particular optical computing device, various types of information about the cement slurry can be ascertained. In some cases, for example, the optical computing devices can be used to monitor a chemical reaction in real-time that relates to cement setting processes, for example, by determining the concentration of unreacted reagents and any resulting products relating to the cement setting process. This may prove advantageous in determining when the cement setting process has progressed to completion. It is known to those skilled in the art that while true completion of cement hydration may take a long time often extending into months, for the purpose of cementing operations (e.g., subterranean cementing operations), the completion of cement hydration is taken as that phase in cement hydration at which point the strength development values (e.g., compressive strength) reach a plateau value, which may, in some instance, take about 2 to about 28 days. In some embodiments, the cement hydration level and indication of strength may be characterized by the concentration cement hydration products, e.g., calcium hydroxide or calcium silicate hydrates in the case of Portland cements. Thus, the systems and methods described herein may be configured to monitor a fluid and a chemical reaction processes related thereto.

As used herein, the term “fluid” refers to any substance that is capable of flowing, including particulate solids, liquids, gases, slurries, emulsions, powders, muds, glasses, combinations thereof, and the like. In some embodiments, the fluid can be an aqueous fluid, including water or the like. In some embodiments, the fluid can be a non-aqueous fluid, including organic compounds, more specifically, hydrocarbons, oil, a refined component of oil, petrochemical products, and the like. In some embodiments, the fluid can be a treatment fluid (e.g., a spacer fluid, a cement fluid composition, a lost circulation treatment fluid, and the like) or a formation fluid as found in the oil and gas industry. Fluids can include various flowable mixtures of solids, liquids, and/or gases. Illustrative gases that can be considered fluids according to the present embodiments include, for example, air, nitrogen, carbon dioxide, argon, helium, hydrogen sulfide (H₂S), methane, ethane, butane, and other hydrocarbon gases, combinations thereof and/or the like.

As used herein, the term “cement fluid composition” refers to any fluid that comprises a cement. Cement is not necessarily hydraulic cement, since other types of materials (e.g., polymers like epoxies and latexes) can be used in place of, or in addition to, a hydraulic cement. Examples of cements may include, but are not limited to, hydraulic cements, Portland cement, gypsum cements, calcium phosphate cements, high alumina content cements, silica cements, high alkalinity cements, shale cements, acid/base cements, magnesia cements (e.g., Sorel cements), fly ash cements, zeolite cement systems, cement kiln dust cement systems, slag cements, micro-fine cements, epoxies, bentonites, latexes, and the like, any derivative thereof, and any combination thereof. Cement fluid compositions may be cement slurries that include water or dry cement blends. Unless otherwise specified, the term “fluid” encompasses cement fluid compositions, the term “cement fluid compositions” encompasses cement slurries and dry cement blends, and the term “cement slurry” encompasses foamed cements. As used herein, the term “dry cement blend” refers to a mixture of solid particles including at least some cement particles and is not hydrated beyond about ambient conditions (e.g., no additional water has been added).

As used herein, the term “chemical reaction process” or “chemical reaction” refers to a process that leads to the transformation of one set of chemical substances to another. As known to those skilled in the art, chemical reactions involve one or more reagents, as described below, that chemically react either spontaneously, requiring no input of energy, or non-spontaneously typically following the input of some type of energy, such as heat, light, or electricity. The chemical reaction process yields one or more products, which may or may not have properties different from the reagents.

As used herein, the term “cement setting process” refers to the chemical reaction(s) that cause a cement slurry to harden into a cement. Chemical reactions of cement setting processes described herein may include, but are not limited to, hydration reactions (e.g., reactions between hydraulic cements and water), crosslinking reactions (e.g., polymer crosslinking reactions and reactions between 2-component epoxies), and the like, and any combination thereof. As used herein, the term “hydraulic cement” refers to a cement that hardens in the presence of water. Changes in characteristics that may be useful in providing the status of a cement setting process may include, but are not limited to, an increase in particle size, a plateau of an exothermic reaction, a decrease in the concentration of a reagent (e.g., water), an increase in the concentration of a product (e.g., a base like calcium hydroxide), and the like, and any combination thereof.

As used herein, the term “cementing operation” encompasses any subterranean operation utilizing a cement slurry, e.g., primary cementing operations, secondary cementing operations, squeeze operations, remedial cementing operations, casing operations, plugging operations (e.g., relative to thief zones), lost circulation operations, zonal isolation operations, and the like including any with traditional or reverse fluid flow directions.

As used herein, the term “characteristic” refers to a chemical, mechanical, or physical property (quantitative or qualitative) of a material of interest (e.g., a spacer fluid, a cement fluid composition, a lost circulation treatment fluid, and the like) or analyte thereof. As used herein, the term “analyte” refers to a chemical component of the material of interest. The term analyte encompasses both chemical components involved in a chemical reaction (e.g., reagents and products) and chemical components not involved in a chemical reaction transpiring within the material of interest. Illustrative characteristics of a material of interest that can be monitored with the optical computing devices disclosed herein can include, for example, chemical composition (e.g., identity and concentration in total or of individual analytes), impurity content, pH, viscosity, density, ionic strength, total dissolved solids, salt content, porosity, opacity, bacteria content, particle size distribution, color, temperature, hydration level, oxidation state, and the like. Moreover, the phrase “characteristic of interest” may be used herein to refer to a characteristic of the cement slurry or analyte thereof, a characteristic of a spacer fluid or analyte thereof, and/or a characteristic of a chemical reaction transpiring or otherwise occurring therein.

Exemplary analytes may include, but are not limited to, water, salts, minerals (wollastonite, metakaolin, and pumice), cements (Portland cement, gypsum cements, calcium phosphate cements, high alumina content cements, silica cements, and high alkalinity cements), fillers (e.g., fly ash, fume silica, hydrated lime, pozzolanic materials, sand, barite, calcium carbonate, ground marble, iron oxide, manganese oxide, glass bead, crushed glass, crushed drill cutting, ground vehicle tire, crushed rock, ground asphalt, crushed concrete, crushed cement, ilmenite, hematite, silica flour, fume silica, fly ash, elastomers, polymers, diatomaceous earth, a highly swellable clay mineral, nitrogen, air, fibers, natural rubber, acrylate butadiene rubber, polyacrylate rubber, isoprene rubber, chloroprene rubber, butyl rubber, brominated butyl rubber, chlorinated butyl rubber, chlorinated polyethylene, neoprene rubber, styrene butadiene copolymer rubber, sulphonated polyethylene, ethylene acrylate rubber, epichlorohydrin ethylene oxide copolymer, ethylene propylene rubber, ethylene propylene diene terpolymer rubber, ethylene vinyl acetate copolymer, fluorosilicone rubber, silicone rubber, poly-2,2,1-bicycloheptene (polynorborneane), alkylstyrene, crosslinked substituted vinyl acrylate copolymer, nitrile rubber (butadiene acrylonitrile copolymer), hydrogenated nitrile rubber, fluoro rubber, perfluoro rubber, tetrafluoroethylene/propylene, starch polyacrylate acid graft copolymer, polyvinyl alcohol cyclic acid anhydride graft copolymer, isobutylene maleic anhydride, acrylic acid type polymer, vinylacetate-acrylate copolymer, polyethylene oxide polymer, carboxymethyl cellulose polymer, starch-polyacrylonitrile graft copolymer, polymethacrylate, polyacrylamide, and non-soluble acrylic polymer), hydrocarbons, acids, acid-generating compounds, bases, base-generating compounds, biocides, surfactants, scale inhibitors, corrosion inhibitors, gelling agents, crosslinking agents, anti-sludging agents, foaming agents, defoaming agents, antifoam agents, emulsifying agents, de-emulsifying agents, iron control agents, proppants or other particulates, gravel, particulate diverters, salts, cement slurry loss control additives, gas migration control additives, gases, air, nitrogen, carbon dioxide, hydrogen sulfide (H₂S), argon, helium, hydrocarbon gases, methane, ethane, butane, catalysts, clay control agents, chelating agents, corrosion inhibitors, dispersants, flocculants, scavengers (e.g., H₂S scavengers, CO₂ scavengers, or O₂ scavengers), lubricants, breakers, delayed release breakers, friction reducers, bridging agents, viscosifiers, weighting agents, solubilizers, rheology control agents, viscosity modifiers, pH control agents (e.g., buffers), hydrate inhibitors, relative permeability modifiers, diverting agents, consolidating agents, fibrous materials, bactericides, tracers, probes, nanoparticles, paraffin waxes, asphaltenes, foams, sand or other solid particles, and the like. Combinations of these components can be used as well.

As used herein, the term “flow path” refers to a route through which a fluid is capable of being transported between two points. In some cases, the flow path need not be continuous or otherwise contiguous between the two points. Exemplary flow paths include, but are not limited to, a slurry tank, a flowline, a pipeline, a conduit, a wellbore annulus (e.g., an annulus between a casing and a wellbore or an annulus between a screen and a wellbore), a casing, a liner, a liner string, a hose, a mixer, a pump, a process facility, a storage vessel, a tanker, a railway tank car, a transport barge or ship, a separator, a contactor, a process vessel, and the like, any hybrid thereof, and any combination thereof. In cases where the flow path is a pipeline, or the like, the pipeline may be a pre-commissioned pipeline or an operational pipeline. It should be noted that the term “flow path” does not necessarily imply that a fluid is flowing therein, rather that a fluid is capable of being transported or otherwise flowable therethrough. In some embodiments, a flow path may be a component of a more complex system, for example, skids, trucks, pumps, and the like. In some embodiments, a flow path may comprise more than one section that is separated, but still fluidly communicable, by apparatuses like valves, flow meters, and the like.

As used herein, the term “electromagnetic radiation” refers to radio waves, microwave radiation, infrared and near-infrared radiation, visible light, ultraviolet light, X-ray radiation, and gamma ray radiation.

As used herein, the term “optical computing device” refers to an optical device that is configured to receive an input of electromagnetic radiation from a fluid or analyte thereof and produce an output of electromagnetic radiation from a processing element arranged within the optical computing device. The processing element may be, for example, an integrated computational element (ICE) used in the optical computing device. As discussed in greater detail below, the electromagnetic radiation that optically interacts with the processing element is changed so as to be readable by a detector, such that an output of the detector can be correlated to at least one characteristic of the fluid, such as a characteristic of a chemical process of interest transpiring in the fluid. The output of electromagnetic radiation from the processing element can be reflected electromagnetic radiation, transmitted electromagnetic radiation, and/or dispersed electromagnetic radiation. Whether reflected, transmitted, or dispersed, electromagnetic radiation is eventually analyzed by the detector and may be dictated by the structural parameters of the optical computing device as well as other considerations known to those skilled in the art. In addition, emission and/or scattering of the substance, for example via fluorescence, luminescence, Raman scattering, and/or Raleigh scattering, can also be monitored by the optical computing devices.

As used herein, the term “optically interact” or variations thereof refers to the reflection, transmission, scattering, diffraction, or absorption of electromagnetic radiation either on, through, or from one or more processing elements (i.e., integrated computational elements). Accordingly, optically interacted light refers to light that has been reflected, transmitted, scattered, diffracted, or absorbed by, emitted, or re-radiated, for example, using the integrated computational elements, but may also apply to interaction with a fluid or an analyte thereof.

The exemplary systems and methods described herein will include at least one optical computing device arranged along or in a flow path in order to monitor a fluid or an analyte thereof flowing or otherwise contained within the flow path. Each optical computing device may include an electromagnetic radiation source, at least one processing element (e.g., integrated computational element), and at least one detector arranged to receive optically interacted light from the at least one processing element. In some embodiments, the exemplary optical computing devices may be specifically configured for detecting, analyzing, and quantitatively measuring a particular characteristic of interest in the flow path. In at least one embodiment, the characteristic may be related to a chemical process of interest (e.g., a cement setting process) and the optical computing devices may be configured to numerically determine the kinetics of reaction in near or real-time. In other embodiments, the optical computing devices may be general purpose optical devices, with post-acquisition processing (e.g., through computer means) being used to specifically detect the characteristic of the fluid or an analyte thereof.

In some embodiments, suitable structural components for the exemplary optical computing devices are described in commonly owned U.S. Pat. No. 6,198,531 entitled “Optical Computational System;” U.S. Pat. No. 6,529,276 entitled “Optical Computational System;” U.S. Pat. No. 7,123,844 entitled “Optical Computational System;” U.S. Pat. No. 7,834,999 entitled “Optical Analysis System and Optical Train;” U.S. Pat. No. 7,911,605 entitled “Multivariate Optical Elements for Optical Analysis System;” U.S. Pat. No. 7,920,258 entitled “Optical Analysis System and Elements to Isolate Spectral Region;” and U.S. Pat. No. 8,049,881 entitled “Optical Analysis System and Methods for Operating Multivariate Optical Elements in a Normal Incidence Orientation;” each of which is incorporated herein by reference in its entirety, and U.S. patent application Ser. No. 12/094,460 entitled “Methods of High-Speed Monitoring Based on the Use of Multivariate Optical Elements;” Ser. No. 12/094,465 entitled “Optical Analysis System for Dynamic Real-Time Detection and Measurement;” and Ser. No. 13/456,467 entitled “Imaging Systems for Optical Computing Devices;” each of which is also incorporated herein by reference in its entirety. As will be appreciated, variations of the structural components of the optical computing devices described in the above-referenced patents and patent applications may be suitable, without departing from the scope of the disclosure, and therefore, should not be considered limiting to the various embodiments or uses disclosed herein.

The optical computing devices described in the foregoing patents and patent applications combine the advantage of the power, precision, and accuracy associated with laboratory spectrometers, while being extremely rugged and suitable for field use. Furthermore, the optical computing devices can perform calculations (analyses) in real-time or near real-time without the need for time-consuming sample processing. In this regard, the optical computing devices can be specifically configured to detect and analyze particular characteristics of interest. As a result, interfering signals are discriminated from those of interest by appropriate configuration of the optical computing devices, such that the optical computing devices provide a rapid response regarding the characteristic of interest as based on the detected output. In some embodiments, the detected output can be converted into a voltage that is distinctive of the magnitude of the characteristic of interest. The foregoing advantages and others make the optical computing devices particularly well suited for field and downhole use.

The optical computing devices can be configured to detect not only the composition and concentrations of an analyte in a fluid, but they also can be configured to determine physical properties and other characteristics of the analyte and/or fluid as well, based on their analysis of the electromagnetic radiation received from the particular analyte and/or fluid. For example, the optical computing devices can be configured to determine a characteristic of interest, e.g., a concentration of a reagent or product, and correlate the determined characteristic to the status of a cement setting process by using suitable processing means. As will be appreciated, the optical computing devices may be configured to detect as many characteristics of interest as desired. All that is required to accomplish the monitoring of multiple characteristics is the incorporation of suitable processing and detection means within the optical computing device for each characteristic of interest, whether pertaining to the fluid or an analyte thereof. In some embodiments, the cement setting status can be determined using a combination of characteristics of interest (e.g., a linear, non-linear, logarithmic, and/or exponential combinations). Accordingly, the more characteristics of interest that are detected and analyzed using the optical computing devices, the more accurately the cement setting status can be determined.

The optical computing devices described herein utilize electromagnetic radiation to perform calculations, as opposed to the hardwired circuits of conventional electronic processors. When electromagnetic radiation interacts with a fluid or analyte thereof, unique physical and chemical information about the material of interest may be encoded in the electromagnetic radiation that is reflected from, transmitted through, or radiated therefrom. This information is often referred to as the spectral “fingerprint” of the material of interest. The optical computing devices described herein are capable of extracting the information of the spectral fingerprint of multiple characteristics of a material of interest (e.g., a cement slurry, a spacer fluid, or an analyte thereof), and converting that information into a detectable output regarding the overall properties of the monitored material of interest. That is, through suitable configurations of the optical computing devices, electromagnetic radiation associated with characteristics of interest in a fluid or analyte thereof can be separated from electromagnetic radiation associated with all other components of the fluid in order to estimate the properties of the monitored substance in real-time or near real-time.

The processing elements used in the exemplary optical computing devices described herein may be characterized as integrated computational elements (ICE). Each ICE is capable of distinguishing electromagnetic radiation related to the characteristic of interest from electromagnetic radiation related to other components of a fluid. Referring to FIG. 1, illustrated is an exemplary ICE 100 suitable for use in the optical computing devices used in the systems and methods described herein. As illustrated, the ICE 100 may include a plurality of alternating layers 102 and 104, such as silicon (Si) and SiO₂ (quartz), respectively. In general, these layers 102, 104 consist of materials whose index of refraction is high and low, respectively. Other examples might include niobia and niobium, germanium and germania, MgF, SiO_(x), and other high and low index materials known in the art. The layers 102, 104 may be strategically deposited on an optical substrate 106. In some embodiments, the optical substrate 106 is BK-7 optical glass. In other embodiments, the optical substrate 106 may be another type of optical substrate, such as quartz, sapphire, silicon, germanium, zinc selenide, zinc sulfide, or various plastics such as polycarbonate, polymethylmethacrylate (PMMA), polyvinylchloride (PVC), diamond, ceramics, combinations thereof, and the like.

At the opposite end (e.g., opposite the optical substrate 106 in FIG. 1), the ICE 100 may include a layer 108 that is generally exposed to the environment of the device or installation. The number of layers 102, 104 and the thickness of each layer 102, 104 are determined from the spectral attributes acquired from a spectroscopic analysis of a characteristic of interest using a conventional spectroscopic instrument. The spectrum of interest of a given characteristic of interest typically includes any number of different wavelengths. It should be understood that the exemplary ICE 100 in FIG. 1 does not in fact represent any particular characteristic of interest, but is provided for purposes of illustration only. Consequently, the number of layers 102, 104 and their relative thicknesses, as shown in FIG. 1, bear no correlation to any particular characteristic of interest. Nor are the layers 102, 104 and their relative thicknesses necessarily drawn to scale, and therefore should not be considered limiting of the present disclosure. Moreover, those skilled in the art will readily recognize that the materials that make up each layer 102, 104 (i.e., Si and SiO₂) may vary, depending on the application, cost of materials, and/or applicability of the materials to the monitored substance.

In some embodiments, the material of each layer 102, 104 can be doped or two or more materials can be combined in a manner to achieve the desired optical characteristic. In addition to solids, the exemplary ICE 100 may also contain liquids and/or gases, optionally in combination with solids, in order to produce a desired optical characteristic. In the case of gases and liquids, the ICE 100 can contain a corresponding vessel (not shown), which houses the gases or liquids. Exemplary variations of the ICE 100 may also include holographic optical elements, gratings, piezoelectric, light pipe, digital light pipe (DLP), variable optical attenuators, and/or acousto-optic elements, for example, that can create transmission, reflection, and/or absorptive properties of interest.

The multiple layers 102, 104 exhibit different refractive indices. By properly selecting the materials of the layers 102, 104 and their relative thickness and spacing, the ICE 100 may be configured to selectively pass/reflect/refract predetermined fractions of electromagnetic radiation at different wavelengths. Each wavelength is given a predetermined weighting or loading factor. The thickness and spacing of the layers 102, 104 may be determined using a variety of approximation methods from the spectrograph of the characteristic of interest. These methods may include inverse Fourier transform (IFT) of the optical transmission spectrum and structuring the ICE 100 as the physical representation of the IFT. The approximations convert the IFT into a structure based on known materials with constant refractive indices. Further information regarding the structures and design of exemplary integrated computational elements (also referred to as multivariate optical elements) is provided in Applied Optics, Vol. 35, pp. 5484-5492 (1996) and Vol. 129, pp. 2876-2893, which is hereby incorporated by reference.

The weightings that the layers 102, 104 of the ICE 100 apply at each wavelength are set to the regression weightings described with respect to a known equation, or data, or spectral signature. Briefly, the ICE 100 may be configured to perform the dot product of the input light beam into the ICE 100 and a desired loaded regression vector represented by each layer 102, 104 for each wavelength. As a result, the output light intensity of the ICE 100 is related to the characteristic of interest. Further details regarding how the exemplary ICE 100 is able to distinguish and process electromagnetic radiation related to the characteristic of interest are described in U.S. Pat. No. 6,198,531 entitled “Optical Computational System;” U.S. Pat. No. 6,529,276 entitled “Optical Computational System;” and U.S. Pat. No. 7,920,258 entitled “Optical Analysis System and Elements to Isolate Spectral Region;” previously incorporated herein by reference.

Referring now to FIG. 2, illustrated is a block diagram that non-mechanistically illustrates how an optical computing device 200 is able to distinguish electromagnetic radiation related to a characteristic of interest from other electromagnetic radiation. As shown in FIG. 2, after being illuminated with incident electromagnetic radiation, a fluid 202 having a characteristic of interest produces an output of electromagnetic radiation (e.g., sample-interacted light), some of which is electromagnetic radiation 204 corresponding to the characteristic of interest and some of which is background electromagnetic radiation 206 corresponding to other components or characteristics of the fluid 202. In some embodiments, the fluid 202 may include one or more characteristics of interest that may correspond to the one or more analytes (e.g., reagents, products, or other chemical components).

Although not specifically shown, one or more spectral elements may be employed in the device 200 in order to restrict the optical wavelengths and/or bandwidths of the system and thereby eliminate unwanted electromagnetic radiation existing in wavelength regions that have no importance. Such spectral elements can be located anywhere along the optical train, but are typically employed directly after a light source, which provides the initial electromagnetic radiation. Various configurations and applications of spectral elements in optical computing devices may be found in commonly owned U.S. Pat. No. 6,198,531 entitled “Optical Computational System;” U.S. Pat. No. 6,529,276 entitled “Optical Computational System;” U.S. Pat. No. 7,123,844 entitled “Optical Computational System;” U.S. Pat. No. 7,834,999 “Optical Analysis System and Optical Train;” U.S. Pat. No. 7,911,605 entitled “Multivariate Optical Elements for Optical Analysis System;” U.S. Pat. No. 7,920,258 entitled “Optical Analysis System and Elements to Isolate Spectral Region;” and U.S. Pat. No. 8,049,881 entitled “Optical Analysis System and Methods for Operating Multivariate Optical Elements in a Normal Incidence Orientation;” and U.S. patent application Ser. No. 12/094,460 entitled “Methods of High-Speed Monitoring Based on the Use of Multivariate Optical Elements;” Ser. No. 12/094,465 entitled “Optical Analysis System for Dynamic Real-Time Detection and Measurement;” and Ser. No. 13/456,467 entitled “Imaging Systems for Optical Computing Devices;” incorporated herein by reference, as indicated above.

The beams of electromagnetic radiation 204, 206 impinge upon the optical computing device 200, which contains an exemplary ICE 208 therein. In the illustrated embodiment, the ICE 208 may be configured to produce optically interacted light, for example, transmitted optically interacted light 210 and reflected optically interacted light 214. In operation, the ICE 208 may be configured to distinguish the electromagnetic radiation 204 from the background electromagnetic radiation 206.

The transmitted optically interacted light 210, which may be related to a characteristic of interest in the fluid 202, may be conveyed to a detector 212 for analysis and quantification. In some embodiments, the detector 212 is configured to produce an output signal in the form of a voltage that corresponds to the particular characteristic of interest of the fluid 202. In at least one embodiment, the signal produced by the detector 212 and the concentration of the characteristic of interest may be directly proportional. In other embodiments, the relationship may be a polynomial function, an exponential function, and/or a logarithmic function. The reflected optically interacted light 214, which may be related to characteristics of other components of the fluid 202, can be directed away from detector 212. In alternative configurations, the ICE 208 may be configured such that the reflected optically interacted light 214 can be related to the particular characteristic of interest, and the transmitted optically interacted light 210 can be related to other components or characteristics of the fluid 202.

In some embodiments, a second detector 216 can be present and arranged to detect the reflected optically interacted light 214. In other embodiments, the second detector 216 may be arranged to detect the electromagnetic radiation 204, 206 derived from the fluid 202 or electromagnetic radiation directed toward or before the fluid 202. Without limitation, the second detector 216 may be used to detect radiating deviations stemming from an electromagnetic radiation source (not shown), which provides the electromagnetic radiation (i.e., light) to the device 200. For example, radiating deviations can include such things as, but not limited to, intensity fluctuations in the electromagnetic radiation, interferent fluctuations (e.g., dust or other interferents passing in front of the electromagnetic radiation source), coatings on windows included with the optical computing device 200, combinations thereof, or the like. In some embodiments, a beam splitter (not shown) can be employed to split the electromagnetic radiation 204, 206, and the transmitted or reflected electromagnetic radiation can then be directed to two or more ICE 208. That is, in such embodiments, the ICE 208 does not function as a type of beam splitter, as depicted in FIG. 2, and the transmitted or reflected electromagnetic radiation simply passes through the ICE 208, being computationally processed therein, before travelling to the detector 212.

The characteristic(s) of interest being analyzed using the optical computing device 200 can be further processed and/or analyzed computationally to provide additional characterization information about the fluid 202 or an analyte thereof. In some embodiments, the identification and concentration of each analyte of interest in the fluid 202 can be used to predict certain physical characteristics of the fluid 202. For example, the bulk characteristics of the fluid 202 can be estimated by using a combination of the properties conferred to the fluid 202 by each analyte.

In some embodiments, the concentration or magnitude of the characteristic of interest determined using the optical computing device 200 can be fed into an algorithm operating under computer control. The algorithm may be configured to make predictions on how the characteristics of the fluid 202 would change if the concentrations of the characteristic of interest are changed relative to one another. In some embodiments, the algorithm can produce an output that is readable by an operator who can manually take appropriate action, if needed, based upon the reported output. In other embodiments, however, the algorithm can take proactive process control by, for example, automatically adjusting the flow of a fluid being introduced into a flow path or by halting the introduction of the fluid in response to an out of range condition, for example, if premature setting is detected.

In some embodiments, the characteristics of interest determined using the optical computing devices 200 can be associated with a timestamp. A timestamp may be useful in reviewing and analyzing the history of the characteristic of interest, which may be of added value in building a library of cement setting processes. In some embodiments, the characteristics of interest, optionally timestamped, can be fed into an algorithm operating under computer control. The algorithm may be configured to make predictions on the status of the cement setting process and/or any operational parameters that need to be changed as described further below. In some embodiments, the algorithm can produce an output that is readable by an operator who can manually take appropriate action, like initiation of a remedial operation, if needed, based upon the output.

The algorithm can be part of an artificial neural network configured to use the concentration of each characteristic of interest in order to evaluate the overall characteristic(s) of the fluid 202 and predict how to modify the fluid 202 in order to alter its properties in a desired way. Illustrative but non-limiting artificial neural networks are described in commonly owned U.S. patent application Ser. No. 11/986,763 entitled “Determining Stimulation Design Parameters Using Artificial Neural Networks Optimized with a Genetic Algorithm,” which is incorporated herein by reference. It is to be recognized that an artificial neural network can be trained using samples of predetermined characteristics of interest, such as known reagents and products resulting from chemical processes involving such reagents, having known concentrations, compositions, and/or properties, and thereby generating a virtual library. As the virtual library available to the artificial neural network becomes larger, the neural network can become more capable of accurately predicting the characteristic of interest corresponding to a fluid or analyte thereof. Furthermore, with sufficient training, the artificial neural network can more accurately predict the characteristics of the fluid, even in the presence of unknown analytes.

It is recognized that the various embodiments herein directed to computer control and artificial neural networks, including various blocks, modules, elements, components, methods, and algorithms, can be implemented using computer hardware, software, combinations thereof, and the like. To illustrate this interchangeability of hardware and software, various illustrative blocks, modules, elements, components, methods and algorithms have been described generally in terms of their functionality. Whether such functionality is implemented as hardware or software will depend upon the particular application and any imposed design constraints. For at least this reason, it is to be recognized that one of ordinary skill in the art can implement the described functionality in a variety of ways for a particular application. Further, various components and blocks can be arranged in a different order or partitioned differently, for example, without departing from the scope of the embodiments expressly described.

Computer hardware used to implement the various illustrative blocks, modules, elements, components, methods, and algorithms described herein can include a processor configured to execute one or more sequences of instructions, programming stances, or code stored on a non-transitory, computer-readable medium. The processor can be, for example, a general purpose microprocessor, a microcontroller, a digital signal processor, an application specific integrated circuit, a field programmable gate array, a programmable logic device, a controller, a state machine, a gated logic, discrete hardware components, an artificial neural network, or any like suitable entity that can perform calculations or other manipulations of data. In some embodiments, computer hardware can further include elements such as, for example, a memory (e.g., random access memory (RAM), flash memory, read only memory (ROM), programmable read only memory (PROM), erasable read only memory (EPROM)), registers, hard disks, removable disks, CD-ROMS, DVDs, or any other like suitable storage device or medium.

Executable sequences described herein can be implemented with one or more sequences of code contained in a memory. In some embodiments, such code can be read into the memory from another machine-readable medium. Execution of the sequences of instructions contained in the memory can cause a processor to perform the process steps described herein. One or more processors in a multi-processing arrangement can also be employed to execute instruction sequences in the memory. In addition, hard-wired circuitry can be used in place of or in combination with software instructions to implement various embodiments described herein. Thus, the present embodiments are not limited to any specific combination of hardware and/or software.

As used herein, a machine-readable medium will refer to any medium that directly or indirectly provides instructions to a processor for execution. A machine-readable medium can take on many forms including, for example, non-volatile media, volatile media, and transmission media. Non-volatile media can include, for example, optical and magnetic disks. Volatile media can include, for example, dynamic memory. Transmission media can include, for example, coaxial cables, wire, fiber optics, and wires that form a bus. Common forms of machine-readable media can include, for example, floppy disks, flexible disks, hard disks, magnetic tapes, other like magnetic media, CD-ROMs, DVDs, other like optical media, punch cards, paper tapes and like physical media with patterned holes, RAM, ROM, PROM, EPROM and flash EPROM.

In some embodiments, the data collected using the optical computing devices can be archived along with data associated with operational parameters being logged at a job site. Evaluation of job performance can then be assessed and improved for future operations or such information can be used to design subsequent operations. In addition, the data and information can be communicated (wired or wirelessly) to a remote location by a communication system (e.g., satellite communication or wide area network communication) for further analysis. The communication system can also allow remote monitoring and operation of a chemical reaction process to take place. Automated control with a long-range communication system can further facilitate the performance of remote job operations. In particular, an artificial neural network can be used in some embodiments to facilitate the performance of remote job operations. That is, remote job operations can be conducted automatically in some embodiments. In other embodiments, however, remote job operations can occur under direct operator control, where the operator is not at the job site (e.g., via wireless technology).

Referring now to FIG. 3A, illustrated is an exemplary system 300 for monitoring a fluid, such as a chemical reaction process that may occur within the fluid and/or to ascertain the location of the fluid, according to one or more embodiments. In the illustrated embodiment, the fluid may be contained or otherwise flowing within an exemplary flow path provided by the casing 304 and/or an annulus 364 defined between the wellbore 360 and the casing 304. In at least one embodiment, the fluid present therein may be flowing in the general direction indicated by the arrows A (e.g., in a reverse cementing operation). As will be appreciated, however, in other embodiments the flow path may be any other type of flow path, as generally described or otherwise defined herein. For example, the flow path may be a storage or reaction vessel and the fluid may not necessarily be flowing while being monitored.

With continued reference to FIG. 3A, the system 300 may include at least one optical computing device 306, which may be similar in some respects to the optical computing device 200 of FIG. 2, and therefore may be best understood with reference thereto. The optical computing device 306 may be housed within a casing or housing (not shown) configured to substantially protect the internal components of the device 306 from damage or contamination from the external environment. The housing may operate to mechanically couple the device 306 to the casing 304 with, for example, mechanical fasteners, brazing or welding techniques, adhesives, magnets, combinations thereof and the like. In operation, the housing may be designed to withstand the pressures that may be experienced within or without the flow path and thereby provide a fluid tight seal against external contamination.

As described in greater detail below, the optical computing device 306 may be useful in determining a particular characteristic of the fluid within the flow path, such as determining a concentration of an analyte (e.g., reagent or product) present within the fluid. In the event the fluid is a cement slurry, knowing the presence and/or concentration of analytes found in the cement slurry may help determine, in some embodiments, (1) the location of the cement slurry (e.g., by monitoring a spacer fluid and/or the cement slurry) and/or (2) the status of the cement setting processes of the cement slurry. Knowing any one of the foregoing may provide guidance to an operator as to parameters of the current operation or subsequent operations. For example, knowing the location of the cement slurry may be useful in determining appropriate pumping speeds of the cement slurry. In other instances, knowing the precise location of the cement slurry as opposed to a generalized calculation of its location (i.e., the location of the cement slurry calculated using, inter alia, the amount of cement slurry introduced, the flow rate, and the estimated volume to be filled) may be used to determine if the amount of cement slurry used in a particular cementing operation should be changed so as to prevent an unnecessary second cementing operation if too little is used. An accurate determination of the location of the cement slurry may also forego the need for remedial operations (e.g., drill-out operations) in the event too much cement slurry is used. In yet other instances, comparing the location of the cement slurry to its calculated location may be useful in determining if damage has occurred to a wellbore, for example, where cement may be leaking or lost into, and perhaps damaging, the adjacent subterranean formation. In other instances, comparing the actual location of the cement slurry to the calculated location may avert losing fluids to the formations by identifying presence of potential thief zones (i.e., natural or man-made high permeability zones such as fractures, vugular zones, or voids) into which large volumes (e.g., <10 to >500 barrels of fluid per hour) of a fluid can be lost. Further, in some reverse cementing operation embodiments, knowing the time of arrival of a cement slurry at the bottom of the casing may be advantageous for preventing entry of excessive amount cement slurry into the pipe that will require a remedial operation, e.g., a drillout.

The device 306 is illustrated in FIG. 3A as an integral part of the casing 304. One skilled in the art would understand that the device 306 may be coupled to the casing 304 so as to be disposed on a surface of the casing 304, partially integrated into a wall of the casing 304, extend outwardly beyond a surface of the casing 304, be flush with a surface of the casing 304, and any hybrid thereof. In some embodiments, the device 306 may be coupled to the casing 304 so as to monitor a fluid in the annulus 364 and/or a fluid in the casing conduit 362.

Referring now to FIG. 3B, with continued reference to FIG. 3A, the device 306 may include an electromagnetic radiation source 308 configured to emit or otherwise generate electromagnetic radiation 310. The electromagnetic radiation source 308 may be any device capable of emitting or generating electromagnetic radiation, as defined herein. For example, the electromagnetic radiation source 308 may be a light bulb, a light emitting device (LED), a laser, a blackbody, a photonic crystal, an X-Ray source, combinations thereof, or the like. In some embodiments, a lens 312 may be configured to collect or otherwise receive the electromagnetic radiation 310 and direct a beam 314 of electromagnetic radiation 310 toward the fluid. The lens 312 may be any type of optical device configured to transmit or otherwise convey the electromagnetic radiation 310 as desired. For example, the lens 312 may be a normal lens, a Fresnel lens, a diffractive optical element, a holographic graphical element, a mirror (e.g., a focusing mirror), a type of collimator, or any other electromagnetic radiation transmitting device known to those skilled in art. In other embodiments, the lens 312 may be omitted from the device 306 and the electromagnetic radiation 310 may instead be conveyed toward the fluid directly from the electromagnetic radiation source 308.

In one or more embodiments, the device 306 may also include a sampling window 316 arranged adjacent to or otherwise in contact with the fluid (e.g., the fluid contained in the flow paths described above in FIG. 3A) for detection purposes. The sampling window 316 may be made from a variety of transparent, rigid or semi-rigid materials that are configured to allow transmission of the electromagnetic radiation 310 therethrough. For example, the sampling window 316 may be made of, but is not limited to, glasses, plastics, semi-conductors, crystalline materials, polycrystalline materials, hot or cold-pressed powders, combinations thereof, or the like. In order to remove ghosting or other imaging issues resulting from reflectance on the sampling window 316, the system 300 may employ one or more internal reflectance elements (IRE), such as those described in co-owned U.S. Pat. No. 7,697,141 entitled “In Situ Optical Computational Fluid Analysis System and Method,” and/or one or more imaging systems, such as those described in co-owned U.S. patent application Ser. No. 13/456,467 entitled “Imaging Systems for Optical Computing Devices,” the contents of each hereby being incorporated by reference.

After passing through the sampling window 316, the electromagnetic radiation 310 impinges upon and optically interacts with the fluid, including any analytes thereof. As a result, optically interacted radiation 318 is generated by and reflected from the fluid. Those skilled in the art, however, will readily recognize that alternative variations of the device 306 may allow the optically interacted radiation 318 to be generated by being transmitted, scattered, diffracted, absorbed, emitted, or re-radiated by and/or from the fluid, or one or more reagents/products present within the fluid, without departing from the scope of the disclosure.

The optically interacted radiation 318 generated by the interaction with the fluid may be directed to or otherwise received by an ICE 320 arranged within the device 306. The ICE 320 may be a spectral component substantially similar to the ICE 100 described above with reference to FIG. 1. Accordingly, in operation the ICE 320 may be configured to receive the optically interacted radiation 318 and produce modified electromagnetic radiation 322 corresponding to a particular characteristic of interest. In particular, the modified electromagnetic radiation 322 is electromagnetic radiation that has optically interacted with the ICE 320, whereby an approximate mimicking of the regression vector corresponding to the characteristic of interest is obtained. In some embodiments, the characteristic of interest corresponds to the fluid. In other embodiments, the characteristic of interest corresponds to a particular analyte (e.g., a reagent or a product) found in the fluid.

It should be noted that, while FIG. 3B depicts the ICE 320 as receiving reflected electromagnetic radiation from the fluid, the ICE 320 may be arranged at any point along the optical train of the device 306, without departing from the scope of the disclosure. For example, in one or more embodiments, the ICE 320 (as shown in dashed) may be arranged within the optical train prior to the sampling window 316 and equally obtain substantially the same results. In other embodiments, the sampling window 316 may serve a dual purpose as both a transmission window and the ICE 320 (i.e., a spectral component). In yet other embodiments, the ICE 320 may generate the modified electromagnetic radiation 322 through reflection, instead of transmission therethrough.

Moreover, while only one ICE 320 is shown in the device 306, embodiments are contemplated herein which include the use of at least two ICE components in the device 306 configured to cooperatively determine the characteristic of interest in the fluid. For example, two or more ICE may be arranged in series or parallel within the device 306 and configured to receive the optically interacted radiation 318 and thereby enhance sensitivities and detector limits of the device 306. In other embodiments, two or more ICE may be arranged on a movable assembly, such as a rotating disc or an oscillating linear array, which moves such that the individual ICE components are able to be exposed to or otherwise optically interact with electromagnetic radiation for a distinct brief period of time. The two or more ICE components in any of these embodiments may be configured to be either associated or disassociated with the characteristic of interest in the fluid. In other embodiments, the two or more ICE may be configured to be positively or negatively correlated with the characteristic of interest. These optional embodiments employing two or more ICE components are further described in co-pending U.S. patent application Ser. No. 13/456,264 entitled “Methods and Devices for Optically Determining a Characteristic of a Substance,” Ser. No. 13/456,405 entitled “Methods and Devices for Optically Determining A Characteristic of a Substance,” Ser. No. 13/456,302 entitled “Methods and Devices for Optically Determining A Characteristic of a Substance,” and Ser. No. 13/456,327 entitled “Methods and Devices for Optically Determining A Characteristic of a Substance,” the contents of which are hereby incorporated by reference in their entireties.

In some embodiments, it may be desirable to monitor more than one characteristic of interest at a time using the device 306. In such embodiments, various configurations for multiple ICE components can be used, where each ICE component is configured to detect a particular and/or distinct characteristic of interest corresponding, for example, to the fluid, a reagent, or a product resulting from a chemical reaction in the fluid. In some embodiments, the characteristic of interest can be analyzed sequentially using multiple ICE components that are provided a single beam of electromagnetic radiation being reflected from or transmitted through the fluid. In some embodiments, as briefly mentioned above, multiple ICE components can be arranged on a rotating disc, where the individual ICE components are only exposed to the beam of electromagnetic radiation for a short time. Advantages of this approach can include the ability to analyze multiple characteristics of interest within the fluid using a single optical computing device and the opportunity to assay additional characteristics simply by adding additional ICE components to the rotating disc corresponding to those additional characteristics.

In other embodiments, multiple optical computing devices can be placed at a single location along the flow path, where each optical computing device contains a unique ICE that is configured to detect a particular characteristic of interest. In such embodiments, a beam splitter can divert a portion of the electromagnetic radiation being reflected by, emitted from, or transmitted through the fluid and into each optical computing device. Each optical computing device, in turn, can be coupled to a corresponding detector or detector array that is configured to detect and analyze an output of electromagnetic radiation from the respective optical computing device. Parallel configurations of optical computing devices can be particularly beneficial for applications that require low power inputs and/or no moving parts.

Those skilled in the art will appreciate that any of the foregoing configurations can further be used in combination with a series configuration in any of the present embodiments. For example, two optical computing devices having a rotating disc with a plurality of ICE components arranged thereon can be placed in series for performing an analysis at a single location along the length of the flow path. Likewise, multiple detection stations, each containing optical computing devices in parallel, can be placed in series for performing a similar analysis.

The modified electromagnetic radiation 322 generated by the ICE 320 may subsequently be conveyed to a detector 324 for quantification of the signal. The detector 324 may be any device capable of detecting electromagnetic radiation, and may be generally characterized as an optical transducer. In some embodiments, the detector 324 may be, but is not limited to, a thermal detector such as a thermopile or photoacoustic detector, a semiconductor detector, a piezoelectric detector, a charge coupled device (CCD) detector, a video or array detector, a split detector, a photon detector (such as a photomultiplier tube), photodiodes, combinations thereof, or the like, or other detectors known to those skilled in the art.

In some embodiments, the detector 324 may be configured to produce an output signal 326 in real-time or near real-time in the form of a voltage (or current) that corresponds to the particular characteristic of interest. The voltage returned by the detector 324 is essentially the dot product of the optical interaction of the optically interacted radiation 318 with the respective ICE 320 as a function of the concentration of the characteristic of interest. As such, the output signal 326 produced by the detector 324 and the concentration of the characteristic of interest may be related, for example, directly proportional. In other embodiments, however, the relationship may correspond to a polynomial function, an exponential function, a logarithmic function, and/or a combination thereof.

In some embodiments, the device 306 may include a second detector 328, which may be similar to the first detector 324 in that it may be any device capable of detecting electromagnetic radiation. Similar to the second detector 216 of FIG. 2, the second detector 328 of FIG. 3 may be used to detect radiating deviations stemming from the electromagnetic radiation source 308. Undesirable radiating deviations can occur in the intensity of the electromagnetic radiation 310 due to a wide variety of reasons and potentially cause various negative effects on the output of the device 306. These negative effects can be particularly detrimental for measurements taken over a period of time. In some embodiments, radiating deviations can occur as a result of a build-up of film or material on the sampling window 316 which has the effect of reducing the amount and quality of light ultimately reaching the first detector 324. Without proper compensation, such radiating deviations could result in false readings and the output signal 326 would no longer be primarily or accurately related to the characteristic of interest.

To compensate for these types of undesirable effects, the second detector 328 may be configured to generate a compensating signal 330 generally indicative of the radiating deviations of the electromagnetic radiation source 308, and thereby normalize the output signal 326 generated by the first detector 324. As illustrated, the second detector 328 may be configured to receive a portion of the optically interacted radiation 318 via a beamsplitter 332 in order to detect the radiating deviations. In other embodiments, however, the second detector 328 may be arranged to receive electromagnetic radiation from any portion of the optical train in the device 306 in order to detect the radiating deviations, without departing from the scope of the disclosure.

In some applications, the output signal 326 and the compensating signal 330 may be conveyed to or otherwise received by a signal processor 334 communicably coupled to both the detectors 324, 328. The signal processor 334 may be a computer including a non-transitory machine-readable medium, and may be configured to computationally combine the compensating signal 330 with the output signal 326 in order to normalize the output signal 326 in view of any radiating deviations detected by the second detector 328. In some embodiments, computationally combining the output and compensating signals 326,330 may entail computing a ratio of the two signals 326,330. For example, the concentration or magnitude of each characteristic of interest determined using the optical computing device 306 can be fed into an algorithm run by the signal processor 334. The algorithm may be configured to make predictions on how the characteristics of the fluid change if the concentration of the measured characteristic of interest changes.

In real-time or near real-time, the signal processor 334 may be configured to provide a resulting output signal 336 corresponding to the characteristic of interest, such as a concentration of a reagent or resulting product present in the fluid. In some embodiments, as briefly discussed above, the resulting output signal 336 may be readable by an operator who can consider the results and make proper adjustments to the flow path or take appropriate action, if needed, based upon the magnitude of the measured characteristic of interest. In some embodiments, the resulting output signal 336 may be conveyed, either wired or wirelessly, to the user for consideration.

Referring now to FIG. 4, illustrated is an exemplary system 400 for monitoring a fluid according to one or more embodiments. In the illustrated embodiment, the system 400 includes a plurality of optical computing devices 406,406′,406″ coupled to a casing 404 in series along the length of the casing 404. Each optical computing device 406,406′,406″ may be similar to the optical computing device 306 of FIGS. 3A and 3B, and therefore will not be described again in detail. Such a plurality of devices 406,406′,406″ may be advantageous to monitor the location and status of fluids during a wellbore operation. For example, illustrated in FIG. 4 is a traditional cementing operation for completing a wellbore 460. As illustrated by arrows A, a fluid (i.e., cement slurry) may flow through the casing conduit 462 change directions at the end of a casing 404 so as to flow through the annulus 464 defined between the wellbore 460 and the casing 404.

As illustrated in FIG. 4, a first device 406″ may be disposed at the end of the casing 404 where the fluid enters the annulus 464. Arranging the first device 406″ at such a location may be advantageous in determining when the fluid has reached the end of the casing 404. Second and third devices 406 and 406′ may be useful in monitoring the location of the fluid as it moves through the annulus 464 and/or the casing conduit 462. In some instances, calculating the actual speed with which the fluid moves through the annulus 464 and/or the casing conduit 462 with the devices 406,406′,406″ may be compared to the calculated speed the fluid should be moving. A slow actual speed may be an indicator that the fluid is being lost into portions of the subterranean formation. Knowing fluid loss is occurring at some point in the wellbore 460 may allow for the operator to change the pumping speeds to minimize fluid loss, or otherwise add additional fluid to the operation to ensure complete and proper placement of a cement slurry. A determination of fluid loss in the wellbore 460 may also provide the operator with an opportunity to proactively alter the properties and/or composition of the fluid being pumped into the wellbore, such as by adding fluid loss control agents, to minimize fluid loss.

As with the embodiments discussed above, the devices 406,406′,406″ may independently include multiple ICE components and be configured to measure one or more characteristics of the fluid in the annulus 464 and the casing conduit 462. Those skilled in the art will readily appreciate the various and numerous applications that the systems 300 and 400, and alternative configurations thereof, may be suitably used with.

Some subterranean operation embodiments of the present invention may involve introducing a fluid or series of fluids (i.e., two or more fluids in series) into a wellbore or an annulus defined therein; optically interacting an electromagnetic radiation source with the fluid and at least one integrated computational element, thereby generating optically interacting light; receiving with at least one detector the optically interacted light; and generating with the at least one detector an output signal corresponding to a characteristic of the fluid.

In some embodiments, the fluid introduced into the wellbore may include a spacer fluid and/or a cement slurry. In some embodiments, the fluid may be a series of fluids, e.g., in order, a flush, a first spacer fluid, a cement slurry, and a second spacer or a displacement fluid.

In some embodiments, a cement slurry may comprise an aqueous fluid, cement particles, and optionally further comprise fillers and/or additives like set-time modifiers and other analytes listed herein. In some embodiments, a cement slurry may be foamed and comprise an aqueous fluid, cement particles, a gas, and a foaming agent and optionally further comprise fillers and/or additives like set-time modifiers and other analytes listed above.

In some embodiments, a spacer fluid may comprise an aqueous fluid, a weighting agent, surfactants, and optionally further comprise additives like salts and other analytes listed above.

In some embodiments, a fluid of interest may comprise a tracer additive having the primary function of being detected by a device comprising the integrated computational element.

Some subterranean operation embodiments of the present invention may involve introducing a fluid or series of fluids into a wellbore or annulus therein; optically interacting light from an electromagnetic radiation source with the fluid and at least one integrated computational element, thereby generating optically interacting light; receiving with at least one detector the optically interacted light; generating with the at least one detector an output signal corresponding to a characteristic of the fluid; and correlating the output signal with a location within the wellbore or annulus therein.

Some subterranean operation embodiments of the present invention may involve introducing a fluid or series of fluids into a wellbore or annulus therein; optically interacting an electromagnetic radiation source with the fluid and at least one integrated computational element, thereby generating optically interacting light; receiving with at least one detector the optically interacted light; generating with the at least one detector an output signal corresponding to a characteristic of the fluid; and changing a parameter of the wellbore operation in response to the output signal. Parameters that are changed may include, but are not limited to, the pumping speed, the amount of fluid introduced, the composition of the fluid introduced, termination of the pumping operation, switching to pumping a displacement fluid or remedial pill (i.e., a small volume of a remedial fluid pumped to repair a damaged zone), and the like, and any combination thereof.

Some subterranean operation embodiments of the present invention may involve introducing a fluid or series of fluids into a wellbore or annulus therein; optically interacting an electromagnetic radiation source with the fluid and at least one integrated computational element, thereby generating optically interacting light; receiving with at least one detector the optically interacted light; generating with the at least one detector an output signal corresponding to a characteristic of the fluid; and correlating the output signal to a cement setting process, examples of which are provided above. In some embodiments, knowing the status of a cement setting process may be used in, inter alia, determining the timing of a subsequent subterranean operation. Performing an operation before the cement has set may cause damage to the cement and necessitate costly remedial operations. In situ monitoring of cement setting processes may eliminate the need for costly and time-consuming wireline logging operations. Further, in situ monitoring may further reduce the time between the cementing operation and a subsequent operation, in that, the cement may set more quickly than expected and in situ monitoring would provide real-time or near real-time data to that effect.

In some embodiments, the output signal may be correlated to both the status of the cement setting process and the location. For example, when flowing a cement it may be useful to know if the cement has begun to prematurely set and where the premature setting is occurring. Premature setting may be caused by the cement slurry encountering an analyte in the wellbore that increases the setting speed and/or encountering higher temperatures. Premature setting may cause formation damage and require remedial operations. Knowing setting has begun during pumping may allow for changing the operational parameters to minimize or eliminate the need for remedial operations.

It should also be noted that the various drawings provided herein are not necessarily drawn to scale nor are they, strictly speaking, depicted as optically correct as understood by those skilled in optics. Instead, the drawings are merely illustrative in nature and used generally herein in order to supplement understanding of the systems and methods provided herein. Indeed, while the drawings may not be optically accurate, the conceptual interpretations depicted therein accurately reflect the exemplary nature of the various embodiments disclosed.

Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present invention. The invention illustratively disclosed herein suitably may be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein. While compositions and methods are described in terms of “comprising,” “containing,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood to set forth every number and range encompassed within the broader range of values. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Moreover, the indefinite articles “a” or “an,” as used in the claims, are defined herein to mean one or more than one of the element that it introduces. If there is any conflict in the usages of a word or term in this specification and one or more patent or other documents that may be incorporated herein by reference, the definitions that are consistent with this specification should be adopted. 

The invention claimed is:
 1. A method comprising: containing a cement slurry within a flow path, the cement slurry having a chemical reaction occurring therein; and optically interacting the cement slurry with an integrated computational element, thereby generating an output signal corresponding to a characteristic of the chemical reaction.
 2. The method of claim 1, wherein the flow path comprises at least one selected from the group consisting of a wellbore, a casing, and an annulus between a wellbore and a casing.
 3. The method of claim 1, wherein optically interacting further comprises reflecting an electromagnetic radiation off of the cement slurry.
 4. The method of claim 1, further comprising: receiving the output signal with a signal processor communicably coupled to the at least one detector; and determining the characteristic of the chemical reaction with the signal processor.
 5. The method of claim 1, further comprising: correlating the output signal with a location of the integrated computational element within the flow path.
 6. The method of claim 1, wherein generating the output signal corresponding to the characteristic of the chemical reaction further comprises determining a concentration of one or more analytes in the cement slurry.
 7. The method of claim 1, the characteristic of the chemical reaction comprises at least one selected from the group consisting of a chemical composition, an impurity content, a pH level, a temperature, a viscosity, a density, an ionic strength, a total dissolved solids measurement, a salt content measurement, a porosity, an opacity measurement, a particle size distribution, any derivative thereof, and any combination thereof.
 8. A method comprising: flowing a series of fluids through a flow path, the series of fluids comprising a spacer fluid followed by a cement slurry; and optically interacting at least one of the series of fluids with an integrated computational element, thereby generating an output signal corresponding to a characteristic of the at least one of the series of fluids.
 9. The method of claim 8 further comprising: correlating the output signal with a location of the at least one of the series of fluids within the flow path.
 10. The method of claim 9 further comprising: changing an operational parameter based on the location of the at least one of the series of fluids within the flow path.
 11. The method of claim 8 further comprising: correlating the output signal with a chemical reaction occurring in the cement slurry.
 12. The method of claim 8 further comprising: performing a remedial operation based on the chemical reaction occurring in the cement slurry.
 13. The method of claim 8 further comprising: changing an operational parameter based on the chemical reaction occurring in the cement slurry.
 14. The method of claim 8, wherein generating the output signal further comprises determining a concentration of one or more analytes in the at least one of the series of fluids.
 15. The method of claim 14, wherein the one or more analytes comprise at least one selected from the group consisting of water, salt, a mineral, wollastonite, metakaolin, pumice, a cement, Portland cement, gypsum cement, a calcium phosphate cement, a high alumina content cement, a silica cement, a high alkalinity cement, a filler, fly ash, fume silica, hydrated lime, pozzolanic material, sand, barite, calcium carbonate, ground marble, iron oxide, manganese oxide, glass bead, crushed glass, a crushed drill cutting, ground vehicle tire, crushed rock, ground asphalt, crushed concrete, crushed cement, ilmenite, hematite, silica flour, fume silica, fly ash, an elastomer, a polymer, diatomaceous earth, a highly swellable clay mineral, nitrogen, air, a fiber, natural rubber, acrylate butadiene rubber, polyacrylate rubber, isoprene rubber, chloroprene rubber, butyl rubber, brominated butyl rubber, chlorinated butyl rubber, chlorinated polyethylene, neoprene rubber, styrene butadiene copolymer rubber, sulphonated polyethylene, ethylene acrylate rubber, epichlorohydrin ethylene oxide copolymer, ethylene propylene rubber, ethylene propylene diene terpolymer rubber, ethylene vinyl acetate copolymer, fluorosilicone rubber, silicone rubber, poly-2,2,1-bicycloheptene, alkylstyrene, crosslinked substituted vinyl acrylate copolymer, nitrile rubber, hydrogenated nitrile rubber, fluoro rubber, perfluoro rubber, tetrafluoroethylene/propylene, starch polyacrylate acid graft copolymer, polyvinyl alcohol cyclic acid anhydride graft copolymer, isobutylene maleic anhydride, acrylic acid type polymer, vinylacetate-acrylate copolymer, polyethylene oxide polymer, carboxymethyl cellulose polymer, starch-polyacrylonitrile graft copolymer, polymethacrylate, polyacrylamide, and non-soluble acrylic polymer), hydrocarbon, an acid, an acid-generating compound, a base, a base-generating compound, a biocide, a surfactant, a scale inhibitor, a corrosion inhibitor, a gelling agent, a crosslinking agent, an anti-sludging agent, a foaming agent, a defoaming agent, an antifoam agent, a emulsifying agent, a de-emulsifying agent, a iron control agent, a proppants or other particulate, a gravel, particulate diverter, a salt, a cement slurry loss control additive, a gas migration control additive, a gas, air, nitrogen, carbon dioxide, hydrogen sulfide, argon, helium, a hydrocarbon gas, methane, ethane, butane, catalyst, a clay control agent, a chelating agent, a corrosion inhibitor, a dispersant, a flocculant, a scavenger, an H₂S scavenger, a CO₂ scavenger, an O₂ scavenger, a lubricant, a breaker, a delayed release breaker, a friction reducer, a bridging agent, a viscosifier, a weighting agent, a solubilizer, a rheology control agent, a viscosity modifier, a pH control agent, a buffer, a hydrate inhibitor, a relative permeability modifier, a diverting agent, a consolidating agent, a fibrous material, a bactericide, a tracer, a probe, a nanoparticle, a paraffin wax, an asphaltene, a foam, sand, and any combination thereof.
 16. A system, comprising: a flow path containing a cement slurry; and at least two optical computing devices arranged in the flow path for monitoring the cement slurry, each of the at least two optical computing devices independently having at least one integrated computational element configured to optically interact with the cement slurry and thereby generate optically interacted light, and at least one detector arranged to receive the optically interacted light and generate an output signal corresponding to a characteristic of the cement slurry.
 17. The system of claim 16, wherein the characteristic of the cement slurry is a concentration of one or more analytes in the cement slurry.
 18. The system of claim 16, wherein the characteristic of the cement slurry corresponds to a reaction occurring within a cement slurry.
 19. The system of claim 16, wherein the characteristic of the cement slurry comprises at least one selected from the group consisting of chemical composition, impurity content, pH, viscosity, density, ionic strength, total dissolved solids, salt content, porosity, opacity, bacteria content, particle size distribution, color, temperature, hydration level, and an analyte oxidation state.
 20. The system of claim 16 further comprising: a signal processor communicably coupled to the at least two optical computing devices for receiving the output signal therefrom, the signal processor being configured to determine a progress of a chemical reaction occurring within the cement slurry. 